3D printing, also known as additive manufacturing (AM), refers to processes used to create a three-dimensional object. A large number of additive processes are available in the current market. The main differences between processes are in the way of depositing layers to create parts and in the used materials. Fused deposition modeling (FDM) is an additive manufacturing technology commonly used for modeling, prototyping, and production applications. In Fused deposition modeling (FDM), the model or part is produced by extruding streams of thermoplastic materials, which harden immediately to form layers. A plastic filament or metal wire is unwound from a coil and supplies material to an extrusion nozzle head (3D printer extruder), which heats the material and turns the flow on and off. Stepper motors or servomotors are typically employed to move the extrusion head. Thereby, the required 3D printing model is obtained after performing the 3D printing process.
Although FDM technique is very flexible for producing 3D model or parts, FDM technique still has some restrictions in the variation of shapes that may be fabricated. For example, it is difficult to produce unsupported stalactites, because the extruding material can't be supported by the printed and hardened parts during the printing process.
For overcoming the above restrictions, the FDM apparatus may dispense multiple materials to produce 3D model or parts during the print process. For example, one main material is employed to build up the model and another auxiliary material is employed as a soluble support structure. The auxiliary material of the soluble support structure is different from the main material of the construction model, and the auxiliary material can be removed after the printing program is executed. Thereby, a 3D model or sample constructed solely by the main material is obtained. In addition, a variety of materials in different colors can be employed for melt-deposition by the FDM apparatus. Therefore, in the mainstream market, a dual printhead assembly of the FDM apparatus is employed to handle different materials at the same time gradually.
A conventional dual printhead assembly of the FDM apparatus includes two single printhead sets jointed together simply. There is no rigid body connected between the two single printhead sets to produce mutual action. When the printhead of the dual printhead assembly needs to be replaced, the two single printhead sets must be adjusted to the same height, and the height difference between the two single printhead sets must be much smaller than the minimum thickness of the FDM printing layer. Hence, it is difficult to execute the installation or adjustment for the conventional dual printhead assembly of the FDM apparatus. Further, the mutual heights of the two single printhead sets are unchangeable and always kept in the same plane during the FDM printing. When the printing program is executed, if the nozzle of another non-use single printhead set scratches the working piece, it will lead to print operations failed. In addition, the conventional dual printhead assembly of the FDM apparatus has the two single printhead sets capable of switching to work alternately. The single printhead set, which is switched from the non-use status to the executable statue, needs to be heated, and another single printhead set, which is switched from the executable status to the non-use status, needs to be cooled. Since the hot material easy to overflow from the nozzle of the single printhead set during cooling, it is necessary to move the dual printhead assembly to a waste box for waiting the temperature to cool down and it must take a lot of time.
Therefore, there is a need of providing a dual printhead assembly and a 3D printing apparatus using the same to overcome the above drawbacks.